Compressor blades in a gas turbine engine can fail, breaking into high velocity projectiles that can damage surrounding engine components. A similar problem with fan blades has been addressed by constructing the fan duct of a composite material.
Stator vanes are employed in gas turbine engines to control the aerodynamic characteristics of compressor blades. The vanes are placed between compressor stages. A typical stator vane is constructed of an alloy. When the vane is struck by a compressor blade fragment, the fragment either ricochets off the vane or fractures the stator blade. Either outcome compounds the problem, possibly subjecting the engine to serious damage. Some stator vanes are constructed completely of a composite material comprising non-metallic fibers in a resin binder. When the vane is intended to rotate, a metal core may be included, giving the vane improved torsional stiffness.
It is known that certain light, low density materials are better suited than other materials, some high density, to stop high velocity objects without being penetrated. The material has the quality to elongate rather than break. This quality is governed by the material's ultimate elongation velocity: ##EQU1## where .rho. is density and E is Young's modulus. In fact, this quality is a primary reason that composite materials such as graphite and epoxy are used on fan ducts or shrouds.